1. Field of the Invention
The invention relates to novel improved cationic surfactants based on quaternary ammonium compounds and the use of such cationic surfactants in industrial cleaner solutions.
2. Discussion of Related Art
For cleaning semi-finished products or finished products in industrial production, for example, automotive parts made of iron or steel, there are used aqueous solutions which contain tensides in addition to further auxiliary materials such as builder substances, complexing agents, organic or inorganic anticorrosive agents and optionally further substances. Thus, processes have been proposed in German Patent Application Nos. 27 12 900 and 32 47 431 wherein quaternary ammonium compounds are used in the alkaline pH range as cationic surfactants besides further cleaner components in which organic residues, more specifically alkyl residues of varying chain lengths, have been bonded to the ammonium nitrogen atom.
Counter-ions of the used ammonium cations include, for example, anions such as chloride, sulfate or methylsulfate which are known as anions that cause corrosion to occur. The necessary content of such anions undesirably promotes the corrosion of equipment parts and treated metal surfaces. This is an extraordinary disadvantage, more specifically in the treatment of metal surfaces with aqueous products, and particularly when the use of higher concentrations of cationics is desired. In fact, corrosion occurs not only over extended periods of time during intermediate storage of treated parts, but also immediately upon treatment of the respective surfaces with the aqueous application solutions.
In German Patent Application No. 30 48 642 there have also been disclosed tenside mixtures for cleaning bottles and other articles having hard surfaces, for example porcelain, china, synthetics, and metal wherein the mixtures contain cationic tensides based on ammonium compounds. However, it is also one disadvantage of these tensides that they contain chloride, bromide or methylsulfate as anions. In this case also, the anions adversely affect the corrosion resistance of parts of the apparatus such as dishwashers and of the treated surfaces as a consequence of the treatment.
Processes for preparing quaternary ammonium compounds which contain at least one long-chain hydroxyalkyl residue by reacting the salt of a tertiary amine and an organic acid in water with a terminal epoxide compound introducing a hydroxyalkyl residue at normal pressure, at a temperature between 40.degree. C. and 100.degree. C. and a pH value of at least 7 are known from German Patent Application No. 33 21 608. However, the resulting quaternary ammonium compounds are also not usable to meet the high requirements set for commercial cationic surfactants with respect to practical servicability and anticorrosive properties. Thus, the anions of numerous organic acids are not suitable as the counter-ions of cationic surfactants, since the resulting quaternary ammonium compounds are poorly soluble in water. Following their preparation, they are obtained in pasty form and, due to their poor solubility in water, cannot be blended in industrial cleansers. It has also been shown that ammonium cations containing numerous hydroxyalkyl groups cause interfering precipitations to occur in water which has not been fully deionized, which fact also renders the use of such cationics impossible. Furthermore, cationic surfactants are often expected to provide a demulsifying and/or defoaming action to emulsions and/or anionic surfactants or emulsifiers, respectively. However, the quaternary ammonium compounds disclosed in said afore-mentioned application have not shown any demulsifying action with respect to emulsions and/or anionic emulsifiers. These disadvantages have also not been compensated for by distinctly improved anticorrosive properties of the produced cationics, as only approximately the same corrosion resistance was obtained as compared with commercially available cationic tensides.
Thus, it is an object of the present invention to provide new improved cationic surfactants based on quaternary ammonium compounds which do not have the disadvantages of the prior art. More specifically, it is an object of this invention to provide cationic tensides useful for industrially applicable cleaning agents the components of which inhibit corrosion, cause a sufficient demulsifying effect to be accomplished with respect to anionic contamination, can be well blended in aqueous industrial cleaners, i.e. are readily water-soluble, do not cause the occurrence of any interfering precipitations, and are compatible with the components conventionally used in industrial cleaners.